This invention relates to a fiber processing line and concerns in particular a method and an apparatus for opening fiber bales placed on a supporting surface in a fiber processing (spinning) plant. The opening (tuft removing) device of a bale opener is moved back and forth above the fiber bales and is, before each pass, lowered for working on the top face of the fiber bale, and the removed fiber tufts are introduced in a storage device from which the tufts are conveyed to a successive processing station. The change in the duration of passes of the opening device is effected by varying the travelling speed of the carriage (trolley) which forms part of the bale opener and which supports the opening device.
According to a known process, a feed adaptation (that is, the adaptation of the vertical thickness of the fiber layer to be removed from the bale top) is effected based on a division of the operation of the opening device into standstill and working periods. A change of the feed adaptation as a function of the maximum or minimum quantity level of the fiber material in the storage device is technologically disadvantageous. The range in which the adaptation may be effected is very small and the fiber output becomes irregular. In order to ensure a uniform fiber quantity removal from the fiber bales, in case of longer standstill periods a greater vertical feed has to be selected which results in larger tufts, whereby a smaller number of passes is required. Conversely, in case of shorter standstill periods, a smaller vertical feed has to be chosen which results in tufts of smaller dimensions requiring an increase of the number of passes. In this manner a compensation for the different densities of the fiber bale in the upper, middle and lower bale zones is sought to be achieved. It is a disadvantage of this process that there is a dependency from a maximum or, as the case may be, a minimum level measurement in the storage device which leads to an inflexibility of the opening process, so that an optimal efficiency of the opening process cannot be achieved.